Brief Statement of Specific Research Goals for the Coming Year Concerning the detailed Characterization of the in vitro Reactions Carried Out by the Six Purified Proteins of the T4 Bacteriophage DNA Replication Apparatus. a) To figure out the role of nucleotide hydrolysis (ATP) by the 44/62 protein in polymerase movement, and of nucleotide hydrolysis (GTP) by the 41 protein in RNA primer formation. b) To identfy and sequence the RNA primer made in vitro, and to map all the sites for RNA primer synthesis on the phiX174 genome. c) To compare the in vitro discrimination against 2-aminopurine triphosphate incorporation into DNA with the same discrimination in vivo and then to identify which T4 protein and cofactors contribute to this discrimination. d) To design an accurate system to measure rare replication errors. This will be based on the biological infectivity of in vitro synthesized phiX174 DNA virus molecules, quantitating the reversion rate of non-viable mutants with known DNA sequence changes. Depending on the mutant used, we can specifically measure base pair transitions, transversions, deletions or additions. BIBLIOGRAPHIC REFERENCES: Alberts, B., Worcel, A. and Weintraub, H. On the biological implications of chromatin structure. Proceedings of the International Symposium on the Eukaryotic Genome. Tehran, in press (1976). Manoil, C., Sinha, N. and Alberts, B. Intracellular DNA-protein complexes from bacteriophage T4-infected cells isolated by a rapid two-step procedure: characterization and identification of the protein components. J. Biol. Chem. 252, 2734-2741 (1977).